There you go again, defensive posture and yelling. I'm starting to worry about this.

If you have an issue with an individual, take it to private messages, do not hijack a post to do so.
Thanks.

As far as figuring out total watts per gallon Oldfishead, indeed, add all the watts together, divide by your tank size. When you feel comfortable with that, we can go into the rather confusing data and info about par and the different types of lighting that is available.

Lighting is not as simple as 25 + 25 = 50. Although we all really wish it would be. Watts is a measure of power consumption not light intensity. A 25W lamp will consume 25W of power over a specific time period. I dont know if its an hour or what that time period is. Two 25W bulbs will consume 25 X 2 or 50W of power over that time period.

This does not mean the total output of the two bulbs is twice that of a single bulb. The intensity will be higher with two bulbs but it wont nessicarly equal that of a single 50W bulb if we continue with our example.

Par is a measure of light intensity. Once you compare PAR output of the same type of bulb and two different wattages you also have to look at the output specitrum. IE the color of the light. You can have two bulbs but one is older than the other. As the bulb ages its PAR may not tail off as much as its desirable specitrum.

You go into even more issues when you look at differnt types of bulbs. Standard incadecent vs florecent vs high output florecent vs compact florecent vs Metal halide.

So the basic answer is 2 X 2 may = 4 but does not mean you will have the same results you would have if you used just one 4 to begin with. IE 4 X 1 = 4

Let me ask this question then. Say you have a 50 inch long tank. On each side you have a 25 watt bulb. On the bottom you have corals, plants, whatever. Would the two 25 watt bulbs on each side be better than the one 50 watt bulb in the middle?

I saw this, and figured I could add a question in with it (hope no one minds). Would 400 watts of metal halide be the same as 400 watts of PC? In the same aspect, would the 400 watts of VHO or T-5's all be the same? If I have a 120 gallon tank, and I want 8 WPG (I'm closer to 8.5, but I want to downsize the 2-400 watt metal halides for power bill reasons), can I get the same coral growth results with just T-5's or VHO's (I'm not too fond of PCs) and not worry about running the metal halides?

I currently have 2-400 watt 20k MH, 1-54 watt pure actinic T-5, 1-54 watt actinic plus T-5, and 2-39 watt pure actinic T-5's, with this rig, can I take out the 2 MH's, and add in 800 watts of T-5's or VHO's, and get the same results?